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Characterization of Propylene Glycol
n-Propyl Ether
Measuring and Modeling of Important Thermodynamic Parameters
Dissertation
zur Erlangung des Grades
Doktor der Naturwissenschaften
(Dr.rer.nat.)
der
Naturwissenschaftlichen Fakult at IV
Chemie und Pharmazie
der Universit at Regensburg
von
Bernhard Ramsauer
REGENSBURG
2010Promotionsgesuch eingereicht am: 30.11.2009
Tag des Kolloquiums 12.01.2010
Die Arbeit wurde angeleitet von: Prof. Dr. W. Kunz
Prufungsaussc hu : Prof. em. Dr. Dr. h.c. J. Barthel, Vorsitzender
Prof. Dr. W. Kunz
Prof. Dr. G. Schmeer
Prof. Dr. J. DaubAcknowledgement
The work of the present dissertation took place between February 2006 and September 2009 at the De-
partment of Chemistry and Pharmacy, Institute of Physical and Theoretical Chemistry, at the University
of Regensburg under the leadership of Prof. Dr. Werner Kunz.
First, I would like to thank Prof. Dr. Werner Kunz for giving me the opportunity to do my Ph.D. in
his labs, his constructive support in di erent ways and for setting up the funding of the work.
I want to express my special gratitude to my little supervisor Dr. Roland Neueder, with whom I spent
many moments in discussing many theoretical as well as experimental aspects. He not only gave me the
opportunity to work with the vapor pressure apparatuses built by himself, but let me participate from
his impressive theoretical, methodological and experimental knowledge on numerous aspects of physical
chemistry. Furthermore he provided me with stimulating and helpful ideas for the every-day lab work.
My hope is that we will climb the Passo dello Stelvio with road bikes in the near future together.
Dr. Andreas Klamt, COSMOlogic GmbH & Co. KG, Leverkusen, broadended my perspective of the
COSMO-RS model simulation during his course held at the University of Regensburg and during his kind
support when preparing and writting a publication manuscript. Connected to this is the indispensable
help of Dr. Sven Hartmann, LTP GmbH, Oldenburg, who I met rst in Cannes. He made it possible
to include UNIFAC calculation within this thesis.
I am grateful for the experience of being part of the institute’s research team. I want to thank in general
all members of the faculty and especially the fellow workers of the mechanical and electronic workshops
for their quick and conscientious settlement of various kinds of work.
Five student assistants devoted themselves to di erent study goals: Markus Karl and Andrea Ho -
mann did a lot of work on the VLE investigations, Hermann Nuss and Julian Kaiser supported
me with experimental help on vapor pressure and heat capacity measurements and nally Monika M.
Meier, who spent so much time and e ort on the conductivity study.
More personally, I would like to thank Dr. Stefan Steve" Thomaier and Dr. Christian Schreini"
" "
Schreiner for their endless motivation, encouragement and sharing all the ups and downs.
Please let me not forget the workhorse of the institute, Wolfgang Wol " Simon . His never ending
"
e ort to get things running and his special kind of humor made this time a special one.
It is very important to emphasis my great time I had in the Oberpfalz students’ hostel, where I have been
living for almost seven years and during which time I got to know so many wonderful people. I want to
thank them for their a ectionate support in all these things that seem to be not directly related to the
performance of a Ph.D. thesis.
Of course I would also like to thank my family for their endless assistance and generous support, without
which I would never have become what I am today and my sister Doris for her help in editing the
pictures.Abbreviations and Physical Constants
Abbreviations
1-HeOH 1-Hexanol
2-BuOH 2-Butanol
COSMO-RS Conductor like screening model - for real solvent
EOS Equation of State
EtOH Ethanol
FID Flame Ionization detector
lcCM low concentration Chemical Model
LCST Lower critical solution temperature
MeOH Methanol
MHC minimum hydrotrope concentration
mod-UNIFAC (Do) modi ed UNIFAC model (Dortmund)
MSA Mean Spherical Approximation
PM 1-Methoxy-2-propanol
PnP 1-Propo
RMS Root mean square
TCD Thermal conductivity detector
VLE Vapor-Liquid Equilibria
Physical Constants
23 1Avogadro’s constant N = 6:022 52 10 molA
23 1Boltzmann’st k = 1:380 54 10 J K
19Electron charge e = 1:602 10 10 C0
12 1 1Vacuum permittivity = 8:854 185 10 C V mol0
1 1Gas constant R = 8:314 33 J K mol
Conversion
31 Torr = 133:32 Pa = 1:3332 10 bar
vList of Symbols
. . . . . . . . . . . . . . . . nonrandomness parameter in NRTL model
0 . . . . . . . . . . . . . . . parameter in COSMO
; . . . . . binary parameters in Wilson equation12 21
1u , u . . . . . . energy in UNIQUAC equation J molij ji
. . . . . . . . . . . . . . . . activity coe cient (on a molal basis)
1 . . . . . . . . . . . . . . . . surface tension N m
1 . . . . . . . . . . . . . . . . speci c conductivity S m
1 2 1; . . . . . . . . . . . molary, limiting molar conductivity S cm mol
1 2 1 . . . . . . . . . . . . . . limiting ionic conductivity S cm mol
1 ; . . . . . . . . . . energy parameters in Wilson equation J molij ji
1 . . . . . . . . . . . . . . . . chemical potential J mol
1 2 . . . . . . . . . . . . . -potential of i in solvent mixture S kcal mol nmi;S
3 1 . . . . . . . . . . . . . . . . molar volume cm mol
, . . . . . . . . . . stoichiometric coe cients+
ex 1 1S . . . . . . . . . . . . . . mean molar excess entropy J K mol
ex 3 1V . . . . . . . . . . . . . mean molar excess volume m mol
1exG . . . . . . . . . . . . . mean molar Gibbs excess energy J mol
1exH . . . . . . . . . . . . . mean molar excess enthalpy J mol
. . . . . . . . . . . . . . . . fugacity coe cient
1 1 . . . . . . . . . . . . . . apparent molar heat capacity J K molc
3 1 . . . . . . . . . . . . . .t molar volume m molv
. . . . . . . . . . . . . . N-particle distribution functionN
. . . . . . . . . . . . . . parameter in COSMOhb
2 . . . . . . . . . . . . . . . charge density of surface segment i e nmi
; . . . . . . . . . . . binary parameter in NRTL modelij ji
. . . . . . . . . . . . . parameter in COSMO
vdW
, . . . . . . . . . . . binary parameters in UNIQUAC equationij ji
. . . . . . . . . . . . . . . area fraction in GC analysisi
2a . . . . . . . . . . . . . . e ective surface area nme
a . . . . . . . . . . . . . interaction parameter of mod. UNIFAC Knm
3 1B . . . . . . . . . . . . . . . second virial coe cient m mol
b . . . . . . . . . . . . . interaction parameter of mod. UNIFACnm
c . . . . . . . . . . . . . . parameter in COSMOhb
1c . . . . . . . . . . . . . interaction parameter of mod-UNIFAC Knm
3d , d . . . . . . . . . . . . pure solvent’s and solution’s density, respectively kg m
f . . . . . . . . . . . . . . . . fugacity Pa
R 1G . . . . . . . . . . . . . . molar residual Gibbs energy J moli
1g ;g . . . . . . . . . . . energy parameters in NRTL model J molig ji
vii3 1K . . . . . . . . . . . . . . association constant dm molA
p . . . . . . . . . . . . . . . . (vapor) pressure Pa
P () . . . . . . . . . . . . -pro le; distribution functioni
vap
p . . . . . . . . . . . . . pure component’s vapor pressure Pai
Q(K) . . . . . . . . . . . relative van-der-Waals surface area of subgroup K
q . . . . . . . . . . . . . . . e ective volume of molecule ii
R(K) . . . . . . . . . . . relative van-der-Waals volume of subgroup K
r . . . . . . . . . . . . . . . e ective size of molecule ii
T . . . . . . . . . . . . . . . temperature K
W (r~;r~ ) . . . . . . . potential of mean force Jij 1 2
x . . . . . . . . . . . . . . . . liquid-phase mole fraction
y . . . . . . . . . . . . . . . . vapor-phase mole
Z . . . . . . . . . . . . . . . compressibility factor
IO.D. . . . . . . . . . . . . optical density: log10 I0
viiiContents
List of Figures xi
List of Tables xv
1. Introduction 1
2. Materials, Puri cation and Analysis 5
2.1. Pure Solvents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.1.1. Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
2.1.2. Propylene Glycol Ethers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
2.1.3. Ethanol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2.2. Electrolytes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2.2.1. Potassium chloride KCl . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2.2.2. Tetrabutylammonium Salts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2.3. Nitrogen Puri cation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
3. Properties and characterization of 1-propoxy-2-propanol / water mixtures 9
3.1. Solubilization curve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
3.2. Surface Tension Measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
3.3. Measurements of Density and Heat Capacity . . . . . . . . . . . . . . . . . . . . . . . . . 12
3.3.1. Experimental . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
3.3.2. Results and Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
4. Vapor-Liquid Phase Equilibria 19
4.1. Fugacity and Activity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
4.2. Calculation of Chemical Potentials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
4.3. Calculation of VLE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
4.4. Bubble-Point Calculations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
4.5. Excess Gibbs Energy Models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
4.5.1. Wilson Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
4.5.2. NRTL Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
4.5.3. UNIQUAC Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
4.6. Data Reduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
4.7. Consistency Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
4.8. Data Processing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
4.9. Measurement Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
4.9.1. Experimental Setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
4.9.2. Exptal Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
4.9.3. Temperature Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
4.10. Analytical Determination of Phase Composition . . . . . . . . . . . . . . . . . . . . . . . . 38
4.10.1. Setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
4.10.2. Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
4.11. Predictive Models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
4.11.1. UNIFAC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
4.11.2. COSMO-RS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
ixContents
4.11.2.1. Theory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
4.11.2.2. Calculation of Phase Equilibria . . . . . . . . . . . . . . . . . . . . . . . . 45
4.11.2.3. Parametrization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
4.12. Discussion of Experimental Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
4.12.1. 1-propoxy-2-propanol + methanol . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
4.12.2.oxy-2-p + ethanol . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
4.12.3. 1-propoxy-2-propanol + 2-butanol . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
4.12.4.oxy-2-p + 1-hexanol . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
4.12.5. 1-propoxy-2-propanol + water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58
4.12.6. 1-methoxy-2-propanol + water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
4.12.7. 1-propoxy-2-propanol + 1-methoxy-2-propanol . . . . . . . . . . . . . . . . . . . . 59
4.13. Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
4.14. Isothermal Vapor-Liquid Equilibria for PnP + ethanol . . . . . . . . . . . . . . . . . . . . 62
4.14.1. Experimental Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
4.14.2. Results and Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
5. Electrical Conductivity in 1-Propoxy-2-propanol 67
5.1. Theoretical Aspects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
5.1.1. Statistical Mechanical Principles . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
5.1.2. Electrostatic Potentials and Ion-Association . . . . . . . . . . . . . . . . . . . . . . 69
5.1.2.1. Debye-Huc kel Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69
5.1.2.2. Chemical Model at Low Concentration . . . . . . . . . . . . . . . . . . . 71
5.1.2.3. Thermodynamics of Association Process . . . . . . . . . . . . . . . . . . . 72
5.1.2.4. Transport Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74
5.1.3. Conductance of Concentrated Solutions . . . . . . . . . . . . . . . . . . . . . . . . 75
5.2. Temperature Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
5.3. Density Measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78
5.3.1. Principle of Density Measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . 78
5.3.2. Measuring Unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78
5.3.3. Execution of Measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80
5.3.4. Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81
5.3.5. Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82
5.3.6. Comparative Study of Literature . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83
5.3.7. Density Coe cients of four Tetrabutylammonium Salts . . . . . . . . . . . . . . . 84
5.4. Relative Permittivity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85
5.4.1. Experimental Set-up . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85
5.4.2. Measuring Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85
5.4.2.1. General Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85
5.4.2.2. Calibration and Evaluation . . . . . . . . . . . . . . . . . . . . . . . . . . 87
5.4.2.3. Possible Sources of Errors . . . . . . . . . . . . . . . . . . . . . . . . . . . 88
5.4.2.4. Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89
5.5. Viscosity Measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90
5.5.1. Principle of Measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90
5.5.2. Instrumentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91
5.5.3. Measuring Unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92
5.5.4. Measurement Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92
5.5.5. Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92
5.5.5.1. Possible Sources of Errors . . . . . . . . . . . . . . . . . . . . . . . . . . . 93
5.5.5.2. Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93
5.5.6. Comparative Study of Literature . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95
5.6. Conductance of Dilute Electrolyte Solutions . . . . . . . . . . . . . . . . . . . . . . . . . . 95
5.6.1. Three-electrode Measuring Cell . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96
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